The VQCP is a high-reliability power supply protection device based on energy storage technology and seamless voltage source switching technique. It uses independent power modules as base units, which can be paralleled to expand capacity according to different requirements. It continuously monitors the system power supply voltage, and upon detecting a deviation from the rated voltage level, the thyristor is disconnected. By controlling the output of the PWM converter and via an injection transformer, it supplies power to the load, ensuring that the protected load is not affected by voltage sags.